Siam Physics Congress 2022 (SPC2022)

Ab-initio study and Atomistic spin model simulations of α-Cr2O3 thin films

S2 Condensed Matter Physics

24 Jun 2022, 14:15

15m

TURQUISE

Board: O-S2-17

Oral Presentation Condensed Matter Physics S2 Condensed Matter Physics

Speaker

Mr Boonthum Kunyangyuen (Chulalongkorn University)

Description

The bulk $C{r}_2{O}_3$ (Chromia) is one of the candidates for voltage-controlled spintronics which is a key element for magnetoelectric random access memory (MERAM) due to its antiferromagnetic and magnetoelectric effects in high temperature. However, engineering applications MERAM require thin films to reduce the voltage required and the chromia films might have different physical and magnetic properties from bulk ones because of film surface effects. Therefore, Density Functional Theory (DFT) study and the Atomistic spin model were used to investigate the effects of bulk and film chromia in this work. The results from DFT calculations showed that the Density of states (DOS) and Band structures of chromia films might be induced by defects and surface interaction with substrates. In order to calculate the Neel temperature ($T_N$) and magnetic properties, we need to extract the exchange interaction constants from the classical Heisenberg model and DFT results, which we evaluated up to the fifth nearest neighbors (J1-J5). Finally, the exchange coupling constants were used as parameters in the atomistic spin model i.e., Monte Carlo simulation and the Landau–Lifshitz–Gilbert (LLG) equation to calculate its magnetic properties such as magnetization ($M$), magnetic susceptibility (${\chi }_M$), $T_N$, and hysteresis loop etc. Moreover, the LLG equation is also used to visualize and simulate spin dynamics of chromia films.

Keywords : Antiferromagnets, Exchange interaction constants, Neel temperature, Atomistic spin model

References
[ 1 ] Saha, C. N. (2020). Fabrication of Micron Scale Test Structures for Magneto-Electric Chromia ($C{r}_2{O}_3$) Thin Films (Doctoral dissertation, State University of New York at Buffalo).
[ 2 ] Sun, C. (2018). Structure Study of Magnetic Thin Films for Voltage Controlled Spintronics by Scanning Transmission Electron Microscopy Experiment and Density Functional Theory Calculations. The University of Wisconsin-Madison.